The Lowdown on Vitamin D

Gregory Plotnikoff, MD, weighs in on the Institute of Medicine’s vitamin D recommendations.

Last winter, the Institute of Medicine (IOM) released a controversial report stating that most North Americans are getting enough vitamin D, that a daily dose of 600 IUs is sufficient for adults and that doses over 4,000 IUs might be harmful. This view ran counter to many other recent studies and created an uproar in nutrition circles. We asked one of our trusted sources, vitamin D expert Gregory Plotnikoff, MD, senior consultant for Allina Center for Health Care Innovation in Minneapolis, to give us his two cents.

First, can you summarize vitamin D’s role in optimizing health?
Vitamin D receptors are found on every tissue in the body, and vitamin D is the primary regulator of more than 600 crucial genes. It helps regulate blood sugar, blood pressure, immune function, pain and inflammation, to name just a few. Consequences of low vitamin D can include depression, metabolic syndrome, muscle weakness,
upper respiratory infection, cardiovascular disease and some cancers. So getting enough vitamin D is crucial.

What do you make of the IOM’s recommendation?
The supporting research is weak, and it left many leading scientists puzzled. Among other problems, it didn’t take into account the location, age or size of the individual. There is no one-size-fits-all when it comes to vitamin D supplementation. The only way to know how much vitamin D you need to take is to get your levels tested.

So are most North Americans getting sufficient amounts of vitamin D?
No. Solid data documents that virtually everyone in North America needs supplementation — all ages and ethnicities and both genders. If you live in a northern climate, it’s even more important. Your body can’t even make vitamin D between November and February if you live above the Mason-Dixon Line.
Is there some safe dose most people could be taking to hedge their bets?
Even the IOM has said that daily dosing up to 4,000 IUs is safe. But not everyone will need that much, and some may need more. Again, the only rational way to dose vitamin D is to get your levels tested. The test is a simple, inexpensive blood draw, and your healthcare practitioner can help you interpret the results. As a baseline, I believe the most advantageous levels of vitamin D are at least 30 nanograms per milliliter of blood. For cancer prevention, the optimal level is higher. Bottom line: If you’re currently taking vitamin D, don’t stop, but do consider getting your levels tested.